Optical synchronizer



3,060,319 OPTICAL SYNCERGNIZER Qrville V. Greunke, Westport, Conn.,assignor to United Aircraft Corporation, East Hartford, Qonn., acorporation of Delaware Filed Dec. 3, 1960, Ser. No. 74,509 Claims. (Si.Z50-219) My invention relates to an optical synchronizer and moreparticularly to a device for generating electrical pulses indicativeofthe position of a scanning beam of energy.

There are many instances in which a beam of energy is employed to scan amedium carrying information to cause a signal to be produced whichrepresents the information. For example, in automatic systems forscoring test papers or for reading ballots or the like, a line oflocations on the medium carrying the information is scanned with a beamof light to determine the location or locations at which marks have beenplaced on the paper. When the beam arrives at a location carrying amark, substantially no or very little light is reilected from the paperand an indication of this fact may be produced by a suitable detectorsuch as a photocell. In order that this information have significance,it is necessary to know not only that a mark is present but also theposition of the scanning beam at the time at which the indication of thepresence of a mark is produced.

An indication of beam position can be obtained by providing a pluralityof photo-sensitive elements at locations corresponding to those at whichmarks may be placed and causing these elements to detect beam position.It will readily be appreciated that a system including a large number ofphoto-sensitive elements is expensive and complicated.

It is possible also that some indication of beam position can beprovided by a signal generated by the means which provides the beam withits scanning motion. This system, however, inherently is relativelyinaccurate since its signal will be a function of the speed and of thelinearity of the scanning motion.

I have invented an optical synchronizer which generates electricalpulses indicative of the position of a scanning beam of energy. Mydevice produces a digital representation of beam position. My opticalsynchronizer requires only a single photo-sensitive element forproducing the required indication of beam position. The indication ofbeam position produced by my optical synchronizer is independent of thespeed and linearity of the scanning motion of the beam.

One object of my invention is to provide an optical synchronizer forgenerating electrical pulses indicative of the position of a scanningbeam of energy in a simple and expeditious manner.

Another object of my invention is to provide an optical synchronizerwhich requires only a single detector for providing the indication ofbeam position.

A further object of my invention is to provide an optical synchronizerfor producing an indication of beam position which is independent of thespeed and linearity of the scanning motion.

Other and further objects of my invention will appear from the followingdescription.

In general my invention contemplates the provision of an opticalsynchronizer including a length of highly refractive transparentmaterial carrying a plurality of energy-responsive means at spacedlocations along its length. In response to a beam of energy traversingthe length, the energy-responsive means causes light to be transmittedalong the length of material to a detector dlg Patented Oct.. 23, 1962rice In the accompanying drawings which form part of the instantspecilication and which are to be read in conjunction therewith and inwhich like reference numerals are used to indicate like parts in thevarious views:

FIGURE 1 is a schematic view illustrating the use of my opticalsynchronizer in an optical scanning system.

FIGURE 2 is a fragmentary view illustrating the mode of operation of myoptical synchronizer.

Referring now to FIGURE 1 of the drawings, in one form of opticalsynchronizer system a beam of light,

indicated by the reference character 10, emanating from a suitable lightsource l2 passes through an aperture 14 in a shield 16 and through acollimating lens 1S to a galvanometer `mirror 2t?. A coil 22mechanically con- 15 nected to mirrr'Z is disposed between the poles 24and 26 of a permanent magnet assembly. The suspension of ,the mirror 2l)includes a restoring coil 28. When a suitable electric current is passedthrough the` coil 22, mirror 2t) oscillates about anwaxis dened by themirror suspension'amanner well known in the art.

After being reilected by the mirror 20, the beam 10 returns through thecollimating lens 18 and strikes the rellecting surface of a mirror 30.As the mirgQLfZO ack and forth along a line on a sheet 32 of paper. Thepaper 32. carries a plurality of spaced locations 34 along the line ofscan of the beam l0. Marks may be placed at predetermined areas of thelocations 34 in any suitable manner known to the art to indicate eitherthe answer to a question or to indicate a choice of candi- 35 make amark, light is reflected from the paper.

location at which the beam is disposed has been marked.

The system thus far described provides information which indicateswhether or not a mark has been placed at the location at which the beampresently is directed. As has been pointed out hereinabove, it isnecessary also to know that position which is being examined by therelatively high index of refraction.

beam at a particular instant.

A second beam 38 of light from the source 12 is l reilected by a mirror40 through a second aperture 42 in the mask 16. Beam 38 passes throughthe lens 18 and to the mirror 20 from which it is reflected back throughthe lens to a mirror 44. Mirror 44 reflects the beam 38 i, and directsit toward my optical synchronizer, indicated generally by the referencecharacter 46. synchronizer 46 includes a rod 48 of a transparentmaterial having a For example, the rod may be formed of a material suchas Lucite, which is the registered trademark of E. I. du Pont de Nemoursand Co. for a strong, transparent and flexible acrylic resin, Plexiglas,which is the registered trademark of Rohm and Haas Co. for athermoplastic colorless translength of the rod 48 of my synchronizer.

rod 48. The lines or grooves 50 are so located that they which producesan electrical signal in response to the transmitted light.

may intercept the beam 3S in certain positions as it moves back andforth along the length of the rod.

osicillatespthe beam '1lb reflected from the mirror`3`0 scans Referringnow to FIGURE 2, it can be seen that when the beam 38 extends in adirection so as to pass between a pair of adjacent marks 50 it passesdirectly through the rod 48. When, however, the beam 38 extends in sucha direction as to impinge on a mark 50, the light is scattered and istransmitted along the length of the rod 48 as indicated by broken linesin the ligure to the ends of the rod. I mount a suitable photonsensitivedevice such, for example, as a photomultiplier 52 adjacent one end ofthe rod. In response to light transmitted along the length of the rodwhen the beam 38 impinges on a mark 50, the photomultiplier 52 isenergized to produce an output signal. It will be appreciated that asthe beam 38 travels along the length of the rod, the photomultiplier 52puts out a series of pulses equal to the number of marks or lines 50etched on the rod. As is explained hereinabove, the marks 50 are sospaced along the length of the rod 48 that each time the beam impingeson a location 34 then at that time the photomultiplier 52 produces anoutput pulse. Any suitable means known to the art may be employed tocount the pulses generated from the point at which one scanning sweepbegins, thus to determine which location is presently being examined bythe beam 10.

While I have so far described my synchronizcr as being responsive tovisible radiation such as will be reflected from the lines or notchesS0, it is to be understood that I could as well make it responsive to abeam of electrons merely by lling the notches with a fluorescentmaterial adapted to produce visible light in response to a beam ofelectrons impinging on the material. It is to be understood further thatthe lines or marks 50 can be regularly or irregularly spaced. They maybe spaced in accordance with some mathematical function or they may bewholly irregular. The duration ot the pulse resulting from theimpingement of the beam 38 on a mark may be regulated by changing theWidth of the lines. It will readily be apparent also that one rod 48 maybe provided with a number of different patterns of lines of marks andthe pattern may be changed merely by rotating the cylinder or rod aboutits axis.

In operation of my optical synchronizcr 40 in the system shown in FIGUREl, the two beams 10 and 38 from the source 12 pass respectively throughapertures 14 and 42, which may be made adjustable and then through thecollimating lens 1S onto the mirror 20 and from the mirror back throughthe lens 18. The reilected beam 10 is directed by the mirror 30 onto thesurface of the paper 32 and, owing to the oscillation of the mirror 20,scans back and forth along the line of locations 34. The reflected beam38 is directed by mirror 44 to the rod 43 and it travels back and forthalong the length of the rod in the same manner as the beam 10 travelsback and forth along the line of locations 34. At times corresponding tothose at which the beam 10 has arrived at the various locations 34, thebeam 3S strikes a mark S0 and detector 52 produces a series of pulseswhich may be counted to indicate the position of the beam 10. When thebeam 10 strikes a location 34 which has been marked, the output of adetector such as the photocell 36 detects the presence of a mark. Thecount of the number of pulses which have been produced by the detector52 indicates the position at which the mark was placed.

It will be seen that I have accomplished the objects of my invention. Ihave provided an optical synchronizer for generating pulses related tothe position of a scanning beam of energy. My system accomplishes thisresult while requiring only a single photosensitive element. Theaccuracy of the indication is independent of the speed or linearity ofthe scanning motion of the beam. My synchronizer produces a digitalindication of the position of a scanning beam which is extremelyaccurate.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of myclaims. It is further obvious that various changes may be made indetails within the scope of my claims without departing from the spiritof my invention. It is, therefore, to be understood that my invention isnot to be limited to the specilic details shown and described.

Having thus described my invention, what I claim is:

1. A radiant energy synchronizcr including in combination a source of ascanning beam of radiant energy, a length of substantially energytransparent material, means for causing said beam longitudinally totraverse said material, means disposed at spaced locations along saidlength of material and responsive to said beam for causing energy -to betransmitted along said material and means responsive to said transmittedenergy for producing a signal representing the arrival of said beam atsaid spaced locations.

2. An optical synchronizcr including in combination a source of ascanning beam of light, a rod of substantially transparent material, aplurality of reflectors disposed in longitudinally spaced relationshipalong said rod, means for causing said beam to traverse said rod wherebyeach of said reilectors causes light to be transmitted along said rod inresponse to impingement of said beam thereon and means responsive tosaid transmitted light for producing a signal indicating the arrival ofsaid beam at said spaced locations.

3. An optical synchronizcr for producing respective irnpulses insynchronism with the arrival of a rst scanning beam of energy atpredetermined positions on a record over which said beam is movedincluding in combination a source of a second scanning beam of energy, alength of substantially transparent material, means for synchronizingthe movement of said scanning beams over said record and along saidlength of material, respective means disposed at longitudinally spacedlocations along said material and responsive to said second beam forcausing light to be transmitted along said material and means responsiveto said light for producing a signal representing the arrival of saidsecond Kbeam at said spaced locations.

An optical scanning system for scanning a plurality of locations on arecord including in combination a rst scanning beam of light, a secondscanning lbeam of light, a length of substantially transparent material,a plurality of reflectors, means positioning said reflectors along saidmaterial at longitudinally spaced locations corresponding to said recordlocations, each of said reflectors causing light impinging thereon to betransmitted along said material, means for moving said beams insynchronism respectively over the record locations to be scanned andover the locations on said material at which said reflectors arepositioned and means responsive to transmitted light for producing aseries of signals representing the arrival of said scanning beam at therespective locations on said medium.

5. In an optical synchronizcr for producing an indication of the arrivalof a irst scanning beam at a plurality of spaced locations disposedalong a line on a form to be scanned, a rst scanning beam of energy, asecond scanning beam of energy, a length of transparent material, `meansdisposed in spaced relationship along said length and responsive toscanning energy impinging thereon for transmitting iight `along saidlength, means for moving said beams synchronously along said line oflocations and along said length of material, and means responsive tolight transmitted along the length of said material for producing anelectrical signal representing the arrival of said first beam at saidspaced locations on said form.

References Cited in the le of this patent UNITED STATES PATENTS1,859,020 Brown May 17, 1932 2,309,117 Iohn Ian. 26, 1943 2,573,373Wales Oct. 30, 1951 2,596,752 Williams May 13, 1952 2,720,810 Senn Oct.18, 1955

